Manually and thermally operable switching device having removable heater element



Nov. 26, 1963 w. A. THOMAS 3,112,385

MANUALLY AND THERMALLY OPERABLE SWITCHING DEVICE HAVING REMOVABLE HEATER ELEMENT I Onginal Filed Jan. 2, 1958 2 Sheets-Sheet l bJlLuAm A.THOMAS BY Arm wzr 2H; H I.

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INVENTOR. IJJILLIAP] A.THOMAS ATTORNEY United States Patent 3,112,385 MANUALLY AND THERMALLY OPERABLE SWITCHING DEVICE HAVING REMOV- ABLE HEATER ELEMENT William Andrew Thomas, South Egremont, Mass., as-

signor to General Electric Company, a corporation of New York Original application Jan. 2, 1958, Ser. No. 706,679, now Patent No. 2,983,804, dated May 9, 1961. Divided and this application Oct. 25, 1960, Ser. No. 64,760

Claims. (Cl. 200-422) This invention relates to electric switching apparatus and more particularly to manually and automatically operable switching devices for controlling motor, lighting, and other low and moderate power electric circuits.

This application is a division of my prior parent application S.N. 706,679, filed January '2, 1958, now Patent No. 2,983,804, entitled Manual Motor Starter.

Small manually and thermally operated switching devices especially those intended to control the operation of small motor circuits are often adapted to be mounted in small metal wall boxes of standard dimensions. It is desirable that the same switching device be usable with circuits having different electrical loads, such as, for example, provided by motors of different horsepower ratings. In this connection, it is also desirable that the heating element with which such devices are provided be easily replaceable and that the rating of the heating element be visible from outside of the housing of the switching device.

Accordingly, an object of theinvention is to provide a manually and thermally operable switching device which may be used to control a wide range of electrical loads by means of interchangeable heating elements which may be quickly and easily inserted within or removed from the switching device by a simple plug-in motion. In furtherance of this object, it is a specific object of the invention to make this heater element accessible and replaceable from the front of the switching device without disconnecting any leads or removing the device from its mounting within an enclosing box.

In accord with one aspect of the invention, a heater element for the thermally responsive element of the switching device is arranged to be plugged into suitable plug-in terminal receiving members on the device through an opening in the front surface thereof. The outer end of the heater element comprises a handle portion that extends beyond the front surface of the device whereby it may be easily grasped manually. The front surface of this handle portion preferably also contains an indication of the heater rating and is adapted to extend through an aperture in the front cover of an enclosing case. With the heater element removed, the terminal receiving members of the device provide convenient means for testing the load current.

The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, together 'with further objects and advantages thereof will be easily understood by referring to the following description taken in connection with the accompanying drawings, in which FIGURE '1 is a perspective view of the switching device mounted within an enclosing box,

FIGURE 2 is a perspective view similar to FIGURE 1 but with the cover of the enclosing box removed to show the switching device itself,

FIGURE 3 is a front view of the switching device of FIGURE 2 with the front housing section removed and a portion of the arc chute broken away,

FIGURE 4-is a sectional view taken along lines 44 of FIGURE 3,

3,112,385 Patented Nov. 26, 1963 ice FIGURE 5 is a sectional view of the switching device taken along lines 5-5 of FIGURE 3,

FIGURE 6 is a transverse plan view of the switching mechanism of the switching device with the housing removed,

FIGURE 7 is a rear view of the front cover of the enclosing box of FIGURE 1,

FIGURE 8 is a detail cross-sectional view of a portion of this front cover, and

FIGURE 9 is a side view of the switching device and front cover showing the connections between the device and the indicating light mounted on the cover.

FIGURE 10 is an exploded perspective view of the operating parts of the switching device of FIGURE 1.

Referringto FIGURES 1 and 2, the invention is shown embodied in a switching device 12 mounted on the side flanges 13A of a base 13 of an enclosing box 14 and having a handle 15 extending through an aperture 16 in the front surface I17 of a wrap-around cover 18 of the enclosing box 14. The front surface 17 of cover 18 also carries an indicating lamp 19 within a semi-cylindrical protective metal jacket 20; the lamp 119 being visible through an aperture 21 in this jacket 20. Jacket 20 may alternatively be a transparent plastic member. The front surface 17 of cover 18 also contains a rectangular aperture 23 through which the front surface of a heater element 24 carried by switching device 12 may be visible.

T he manner by which indicating lamp 19 receives power from the switching device 12 is shown in FIGURES 7 and 9. The insulated wireleads 26, 27 of lamp 19 ex tend through holes 28 in cover 18 and connect to terminal strips 29 and 30 having a central portion located between split into :a top or front portion 40 and a bottom or rear portion 41. with a deep central recessed portion 42 and a pair of shallower recessed opposite side portions 43 and 44. A switch operating mechanism 45, to be described in greater detail hereinafter, is located within the deep central recessed portion 42 while a switching assembly including the arc chutes 46 and contact carrying members are located within the shallower side portions 43 and 44. Line terminals 48 and 49 located on a shelf 50 formed integral with rear housing portion 41 are oriented to receive wires 51 threaded into the terminals through holes 52 in the rear of shelf '50. The terminal lugs are fastened to wires 51 by terminal screws 53 tightened by screw drivers inserted through holes 5-4 in the sides of the insulated housing. The load terminals 55, 56 are likewise located on shelves '57 formed integral with the housing portion 41 at the opposite end from the line terminals 48, 49. These terminals are likewise oriented to receive wire connections through the rear of the shelves 57 but are tightened down by the insertion of screw drivers into holes 58 in the upper end wall of the housing. Both the line and load terminals, as well as the switching mechanism and are chutes are trapped in place by the front cover portion 40 of the insulating housing 39. The front and rear portions 40 and 41 of insulating housing 39 are fastened together by bolts 60 inserted through suitable registering apertures at opposite ends and threaded into mounting lugs 61.

A small self-contained manually and thermally actuated switch operating mechanism is provided wherein the switching member has its contact actuating end portion Bottom portion 41 is generally cup-shaped swingable across the mechanism immediately beneath the operating handle. This enables the movable contactcarrying members which are actuated by this switching member to be located on opposite sides of the switching mechanism close to the front of the housing, thereby permitting the shallow depth dimension of side housing portions 43, 44. Referring particularly to FIGURES 5, 6, and 10, the switch-operating mechanism comprises a U-shaped metal frame 65 having side arms 66, 67 between which the components of the mechanism are mounted. The operating member for the switch is pivoted at the upper end of frame 65 and includes the handle and a metal arm 68 which extends to a point adjacent the bottom of frame 65. A thermally responsive element in the form of an L-shaped bi-metal strip 69 is attached to the base of frame 65 and extends upwardly at one side of the mechanism between the arms 66 and 67. A carrier member 70 having V-shaped side arms is pivoted between arms 66 and 67 by pins 71 at the opposite upper side of the frame. Carrier member 70 contains an overhanging lip or projection 72 at one upper end which rests upon the upper free end of bimetal strip 69 in latched engagement therewith. A switching member 73 has a pair of downwardly depending arms which are pivoted at their lower end upon the V-shaped notches formed by the V- shaped arms of triangular carrier member 70. The switching member 73 contains an upper switch actuating portion 76 which extends laterally through suitable apertures in the side walls 66 and 67 of frame member 65. This upper switching portion 76 is swingable across the switching device along an arc beneath handle 15 and generally parallel with the front surface of the device. An operating over-center spring 77 is connected between the operating arm '68 and the center of the switch actuating portion 76 of switching member 73.

The laterally extending ends 78, 79 of switching member 73 enter within arc chutes 46 and pass through slots 80 in movable insulated contact carriers 81, best seen in FIGURES 4, 6 and 10. A bridging contact member 82 is mounted on contact carrier 81 by springs 83 and is arranged upon lateral movement of contact carrier 81 to engage a pair of stationary contacts 84, 85. The swinging movement of switching member 73 upon operation of handle 15 causes a lateral reciprocation of contact carrier 81 to make and break the electrical connection between stationary contacts 84 and 85 by virtue of the engagement therewith by contact bridging member 82.

The upper stationary contacts 84 on each side of the switching mechanism are connected to the line terminals 48 and 49 respectively. The lower stationary contact 85 of one pole of the switch is connected by a first strip member 87 passing beneath its adjacent arc chute 46 directly to one load terminal 55 of the switch. In accordance with the invention to which the present divisional application is directed, the other lower stationary contact 85A in the other pole of the switch is connected by another strip 88 passing beneath the other arc chute 46 to a lower plug-in terminal receiving member or jack 89 for the heater element 24. Connector strips 87 and 88 also contain upwardly extending portions 87A and 88A which terminate within recesses 37, 38 in the front surface of the switching device thereby to engage and supply power to the indicating light through the terminals 34, 35 carried by the under surface of the front cover of the enclosing case.

Lower jack 89 is located on the bottom of recessed centr-al portion 42 in a compartment 94 alongside bi-metal 69. The jack comprises a generally U-shaped metal strip 90 formed integral with conducting strip 88 and a spring biased metal clip 91 extending through an -L-shaped aperture in the U-shaped strip 90. The upwardly extending leg portion 96 of U-shaped strip 90 is supported against a ridge 92 in the end wall 93 of the insulating housing. The lower end 95 of plug-in heater 24 is received between one leg 96 of U-shaped metal strip 90 and spring biased metal clip 91.

Plug-in heater 24 has a generally T-shaped configuration with a plastic handle portion 100 adapted to extend beyond the front surface of the insulating housing 40 when the heater 24 is plugged into compartment 94. The heater contains a generally T-shaped metal base strip 101 having its head portion embedded within plastic handle portion 100 and having its elongated stem portion covered on opposite sides by mica insulating sheets 102. Strip 103 is wrapped around the lower end 95 of heater 24 and a coiled heating resistance wire I104 surrounds the mica insulating sheets 102 and has one end connected at 105 to the conducting end strip 103. The other end of heating coil 104 is connected to a shoulder terminal 106 of the metal base strip 101. Shoulder terminal 106 is adapted to be received within an upper plug-in terminal receiving member or jack 107 carried by and connected to load terminal 56, as best seen in FIGURES 3 and 5. The electrical circuit for heater 24 when plugged into compartment 94 is thus from line terminal 49 through stationary and movable contacts 84, 82 and 85A and thence through conducting strip 88 to lower jack 89', lower heater terminal 103, heating coil 104, upper shoulder terminal 106 of heater 24 and jack 107 to load terminal 56.

Upper jack 107 includes a pair of contact jaws 108 and 109'; jaw 108 being formed integral with load terminal 56 and jaw 109 being clamped against jaw 108 by a U- shaped metal spring clip 110. The shoulder terminal 106 of heater 24 is adapted to be received between the contact jaws 108, 109 during plug-in motion of the heater 24. The shape and location of the resistance wire in the heating element as well as the number of turns and type of wire may, of course, be varied to give different desired heating characteristics with different currents passing through the heating device as a result of different loads connected thereto.

In the utilization of switching device 12, a heater element 24 having a heating characteristic designed to match the desired load to he switched is first plugged into compartment 94 within switch 12. The load and line terminals of the two poles of the device are then connected in the circuit to be controlled and the switching device mounted on the end flanges 13A of the wall box 14. The wrap-around cover 18 of the wall box is then mounted in place by screws 1'15 thereby bringing indicating lamp terminals 34 and 35 into engagement with the upper ends 87A, 88A of the conducting strips 87, 88 within recesses 37 and 38 of the switching device 12. Operation of handle 15 causes the lower end of operating arm 68 to carry the over-center spring 77 across the pivot of switching arm 73 in the V notches of carrier 70 thereby to swing the upper portion of switching arm 73 with a snap action. The movement of switching arm 73 impels a corresponding snap opening and closing movement of the stationary and movable contacts 82, 84 and 85 within the arc chutes 46. The closure of these contacts delivers current between the line and load contacts of each pole of the switch and through the heater 24 in series with one pole of the switch. Current is also delivered to the upper ends 87A, 88A of the connecting strips 87, 88 thereby to supply power to the indicating lamp whenever the switch is closed, whose magnitude depends upon the voltage difference between the two poles of the line. Indicating lamp 19 may conveniently have a current limiting resistor 116 connected in parallel or in series therewith to protect the lamp against burn out due to excessive voltages or currents.

In the event of an overload or short circuit in the circuit controlled by switching device 12, the greater current flowing through heater element 24 will cause the bi-metal 69 to deflect toward the heater and unlatch the carrier member 70 from the upper end of the bi-metal. The carrier member will then swing downward about its pivot 71 as the result of the force of over-center spring 77 upon the carrier through the switching arm 73 and this downward pivotal motion of carrier '71 will carry the switch actuating end of the switching arm 73 downward and across the face of the switching device 12 thereby to open the switching contacts 32, 84 and 85. This tripping motion of the carrier 70 also carries the operating arm 68 to an intermediate position between its off and on position thereby to move the handle 15 to an intermediate trip indicating position. Upon clearing of the fault in the line and cooling of bi-metal 69, the switching device may be reset by moving the handle back to the off position; an extension arm 117 of operating member 63 serving to engage a projection 118 upon carrier member 70 to enforce this resetting movement of the carrier member 7th If it should thereafter be desired to use the switching device 12 with a load of different rating, the cover 18 of the closing box is removed, and the heater element 24 is merely pulled out and replaced by a heater of different rating without the necessity for disconnecting the switching device or removing any portion of its housing,

Although I have described a specific embodiment of my invention, many modifications may be made, and I intend, therefore, to cover by the appended claims all such modifications as fall Within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the Uni-ted States is:

1. An electric switching device comprising a housing, switching contacts, a switching mechanism for switching contacts in said housing having an operating handle extending through the front surface of said housing, said housing having an aperture opening at the front surface thereof, a thermally responsive element within said housing alongside said aperture for operating said switching mechanism independent of said operating handle, an electric heating element removably positioned within said aperture and having an insulating handle projecting from said aperture at said front surface, and means for plug-in mounting of said heating element including terminals connected in circuit with said switching contacts frictionally retaining said heating element within said aperture alongside said thermally responsive element, said heating element being separate from said switching contacts and being installed and removed with respect to said housing solely by movement thereof into and out of said aperture relative to said terminals and relative to said switching contacts without disturbing said housing and said switching contacts.

2. An electric switching device comprising a housing, stationary switching contacts, a switching mechanism for opening and closing said switching contacts in said housing having an operating handle extending through the front surface of said housing, a thermally responsive element within said housing for operating said switching mechanism and extending generally from front to rear of said housing, said housing having an aperture extending from front to rear thereof and opening at the front sur face thereof, an electric heating element having plug-in terminals and having a handle portion, and means for plug-in mounting said heating element within said aperture alongside and in heating relation with said thermally responsive element with said handle portion extending through the front surface of said housing, said last-named means including fixed terminals connected in circuit with said switching contacts and making frictional electrical contact with said plug-in terminals, said heating element being separate from said switching contests and being installed and removed with respect to said housing solely by movement thereof into and out of said aperture relative to said switching contacts and relative to said fixed terminals Without disturbing said housing and said switching contacts.

3. An electric switching device comprising a housing, switching contacts, a switching mechanism for said switching contacts within said housing, a thermally re- 6 sponsive element within said housing for operating said switching mechanism, terminal jacks within said housing connected in circuit with said contacts, said housing having an aperture opening at the front surface thereof,

an electric heating element having plug-in terminals engaging said jacks and mounted thereby in said apertures alongside said thermally responsive element, said heating element having a handle portion extending through the front of said housing, said heating element being installed and removed with respect to said housing by movement thereof into and out of said aperture relative to said switching contacts and relative to said jacks without disturbing said housing and said switching contacts.

4. An electric switching device comprising a housing, switching contacts within said housing, a mechanism for opening and closing said switching contacts and having an operating handle extending through the front of said housing, a bi-metal strip for operating said mechanism independent of said handle extending within said housing in a direction from front to rear thereof, said housing having an aperture opening at the front thereof, an elongated electric heating element having a handle portion at one end and having plug-in terminals spaced generally in the direction of its length, and means for mounting said heating element in said aperture alongside said bi-metal strip Within said housing with said handle portion extending through the front of said housing, said mounting means including fixed terminals spaced in the direction from front to rear of said housing frictionally engaging said plug-in terminals and connected in circuit with said switching contacts said heating element being separate from said switching contacts and being installed and removed with respect to said housing solely by movement thereof into and out of said aperture relative to said switching contacts and relative to said fixed terminals without disturbing said housing and said switching contacts.

5. An electric switching device comprising a housing, a pair of stationary switching contacts within said housing, a mechanism for opening and closing said contacts having a handle extending through the front of said housing, load and line terminals for said device, a bimetal strip within said housing for operating said mechanism, said housing having an aperture opening at the front thereof, an electric heating element having a handle portion and plug-in terminals, and means for plugin mounting said heating element in said aperture alongside said strip with its handle portion extending outside of said housing, said mounting means including a first fixed terminal frictionally engaging one of said plug-in terminals and connected to one 'of said switching contacts and a second fixed terminal f-rictionally engaging the other of said plug-in terminals and connected to one of said load and line terminals said heating element being separate from said switching contacts and being installed and removed with respect to said housing solely by movement thereof into and out of said aperture relative to said switching contacts and relative to said fixed terminals without disturbing said housing and said switching contacts.

References Cited in the file of this patent UNITED STATES PATENTS 2,056,119 Bentley Sept. 29, 1936 2,094,964 Sachs Oct. '5, 1937 2,185,525 Sachs Jan. 2, 1940 2,248,017 Cohen July 1, 1941 2,505,326 Jackson Apr. 25, 1950 2,611,055 Webster Sept. 16, 1952 2,629,796 Kern Feb. 24, 1953 2,705,310 Hodge Mar. 29, 1955 2,831,935 Page Apr. 22, 1958 

1. AN ELECTRIC SWITCHING DEVICE COMPRISING A HOUSING, SWITCHING CONTACTS, A SWITCHING MECHANISM FOR SWITCHING CONTACTS IN SAID HOUSING HAVING AN OPERATING HANDLE EXTENDING THROUGH THE FRONT SURFACE OF SAID HOUSING, SAID HOUSING HAVING AN APERTURE OPENING AT THE FRONT SURFACE THEREOF, A THERMALLY RESPONSIVE ELEMENT WITHIN SAID HOUSING ALONGSIDE SAID APERTURE FOR OPERATING SAID SWITCHING MECHANISM INDEPENDENT OF SAID OPERATING HANDLE, AN ELECTRIC HEATING ELEMENT REMOVABLY POSITIONED WITHIN SAID APERTURE AND HAVING AN INSULATING HANDLE PROJECTING FROM SAID APERTURE AT SAID FRONT SURFACE, AND MEANS FOR PLUG-IN MOUNTING OF SAID HEATING ELEMENT INCLUDING TERMINALS CONNECTED IN CIRCUIT WITH SAID SWITCHING CONTACTS FRICTIONALLY RETAINING SAID HEATING ELEMENT WITHIN SAID APERTURE ALONGSIDE SAID THERMALLY RESPONSIVE ELEMENT, SAID HEATING ELEMENT BEING SEPARATE FROM SAID SWITCHING CONTACTS AND BEING INSTALLED AND REMOVED WITH RESPECT TO SAID HOUSING SOLELY BY MOVEMENT THEREOF INTO AND OUT OF SAID APERTURE RELATIVE TO SAID TERMINALS AND RELATIVE TO SAID SWITCHING CONTACTS WITHOUT DISTURBING SAID HOUSING AND SAID SWITCHING CONTACTS. 